The present invention relates generally to an apparatus and method for the nondestructive readout of a latent electrostatic image formed on an insulating material. More particularly, the present invention relates to a method and apparatus for reading out a latent electrostatic image formed on a sheet or layer of insulating material by inducing a surface depletion layer on a sheet or layer of semiconducting material that is conductive in the dark (or a change in an already existing surface depletion layer on the semiconducting material) that is related to the latent electrostatic image and then reading out the accumulated charges in the surface depletion layer so formed on the semiconducting material using the surface photovoltage effect.
The invention is especially useful in reading out a latent electrostatic image formed on an insulator by irradiation with X-rays but is not exclusively limited to an electrostatic image formed by that type of radiation.
References of interest include U.S. Pat. No. 3,199,086 to Kallmann et al; U.S. Pat. No. 3,691,376 to Bauerlien et al; U.S. Pat. No. 3,859,527 to Luckey; U.S. Pat. No. 4,176,275 to Korn et al; U.S. Pat. No. 4,296,478 to Kiess et al; U.S. Pat. No. 4,319,284 to Kiess et al; U.S. Pat. No. 4,404,422 t Green et al and U.S. Pat. No. 4,508,966 to Oberschmid et al.